JSON Validator

How to Use

1. Paste your JSON into the input area.
2. Click Validate to check for errors.
3. If valid, use Format if Valid to beautify it.

Common JSON Syntax Errors

• Trailing commas: [1, 2, 3,] — the comma after 3 is invalid.
• Single quotes: {'name': 'test'} — JSON requires double quotes.
• Unquoted keys: {name: "test"} — all keys must be double-quoted.
• Missing commas: Forgetting commas between properties or array elements.
• Comments: JSON does not support // or /* */ comments.

Why Validate JSON?

JSON validation catches syntax errors before they cause runtime failures in your application. A single misplaced comma or missing quote can cause an entire API response to fail parsing, a configuration file to be rejected, or a data pipeline to break. Validating JSON during development saves debugging time and prevents production incidents.

Common sources of invalid JSON include: copying from documentation that uses single quotes or trailing commas (valid in JavaScript but not JSON), manually editing JSON files and accidentally breaking the structure, and text editors that insert smart quotes or special characters. This validator provides specific error messages with line and column numbers to help you pinpoint and fix issues quickly.

JSON Validation vs. Schema Validation

Syntax validation (what this tool does) checks whether a string is valid JSON — are the brackets matched? Are strings properly quoted? Is the overall structure correct? It answers the question: "Is this valid JSON?"

Schema validation goes further by checking whether the JSON conforms to a specific structure. A JSON Schema defines which fields are required, what data types they must be, value constraints (minimum, maximum, pattern), and nested object structures. Tools like AJV (for JavaScript) and jsonschema (for Python) perform schema validation. This tool focuses on syntax validation as the essential first step.

How JSON Parsing Works

This validator uses the browser's native JSON.parse() function, which is the same parser used by JavaScript runtimes in production. When parsing fails, JSON.parse() throws a SyntaxError with a message indicating the position of the error. This tool extracts that position information and displays it in a human-readable format, making it easy to locate and fix the problem.

Tips for Working with JSON

• Use a code editor with JSON syntax highlighting to catch errors as you type
• When debugging API responses, paste the raw response here to check for validity before processing
• If you need comments in configuration, consider JSON5 or JSONC formats (supported by VS Code and some tools)
• For large JSON files, format them first with our JSON Formatter to make the structure visible, then validate
• When constructing JSON programmatically, always use JSON.stringify() rather than string concatenation to avoid syntax errors

Related Tools

Once validated, beautify with the JSON Formatter. Convert to CSV with the JSON to CSV Converter or to YAML with the JSON-YAML Converter. Encode for URLs with the URL Encoder or as text with the Base64 Encoder. Compare JSON versions with the Diff Checker.